But Roger,

 

    Once you have the e-less copper <or DM> coverage and panel

strike plate I have seen the <pattern> plate rob from the bottom

and plate the knees of the hole producing a week connection when 

we go higher than 1:1. (Like a little isolated plating cell).

It also appears that once the hole hits a certain size, these limitations

are not so much an issue <?????????>. Also, if the hole bottom is

not conductive, like accidently covered with photoresist, sometimes

the plating covers all the way down <????????>. Sounds like a chemistry

supplier DOE to me. Please include ASF in the matrix too!

 

Groovy

 

[log in to unmask] wrote:
> 
> A 1:1 aspect ratio for blind vias should not be considered the limit.
> 
> There are some DM processes that can "coat" blind vias to make them
> conductive rather than rely on the electroless copper process to get into the
> bottom of the hole.  Since the gassing of electroless copper precludes going
> much higher than a 1:1 aspect ratio, i.e.the gassing limits deposition in the
> bottom of a blind via, the next limitation becomes that of electrodeposition
> itself.  Providing the entire hole is conductive, I've seen aspect ratios of
> closer to 2:1 for blind vias.  And that's only with conventional
> electroplating technology.
> 
> Imagine the possibilities when the industry gets to working more on the
> electroplating aspects of blind via board construction.
> 
> Roger Mouton
> INSULECTRO
> Lake Forest, CA
> 
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